Presentations

PDH - As per Pennsylvania's PE Act 25 Section 4.5c (d) (iv);One hour of professional development in course work, seminars or professional, technical presentations made at meetings, employer-sponsored courses, conventions or conferences shall equal one PDH unit. Note that it is the applicant’s responsibility to track their participation. This form is provided for your convenience.

Cutoff walls are widely used as subsurface, vertical engineered barriers for controlling and diverting groundwater flow and containing subsurface pollutants. Soil-bentonite (SB) cutoff walls constructed with backfills containing bentonite (a high swelling clay) are the most common type of vertical barrier used to control contaminant migration. The SB backfill mixtures are primarily designed for constructability and low hydraulic conductivity to minimize advective transport. Although diffusion has been recognized as a significant contaminant transport mechanism in SB cutoff walls, there is limited information regarding diffusion properties of SB backfills. Also, utilizing onsite soils and minimizing bentonite addition to the backfill is preferable, as long as the required engineering properties can be achieved. However, only a limited range of SB backfill compositions have been evaluated in previous experimental work. In this study, a novel testing technique was used to measure diffusion properties of two SB backfills with different percentages of bentonite. One backfill was prepared in the laboratory using a clean sand, whereas the other backfill was sampled from a constructed cutoff wall that used onsite soils. The test methods and preliminary results will be presented. The results of the study will advance our understanding of contaminant transport through SB backfills and improve the ability to predict the rate at which contaminants migrate through vertical environmental containment systems.

The Villanova Urban Stormwater Partnership (VUSP) has been intensively monitoring stormwater control measures (SCMs) at the headwaters of the Jenkintown Creek. The SCMs consist of two rain gardens, riparian buffers, and a bioretention basin. Both water quality (e.g. temperature, TSS, TDS, and nutrients) and water quantity (inflow, outflow, depth, and velocity downstream) are being monitored. Data collected from 2 years of monitoring will presented and trends will be discussed.

The objective of the proposed research is to model volume reduction green infrastructure (GI) practices at a very fine scale. GI are a solution to highly urbanized communities, allowing them to reduce stormwater flow volumes and mitigate pollutants. This research models stormwater drainage networks (containing traditional and GI stormwater systems). This allows for hydrologic comparison between GI and stormwater infrastructure with hard designs. The modeling is done in ArcGIS, a geospatial data model used for delineating the flow accumulation lines and urban catchments using the Spatial Analyst tool. The input data for this model is a uniquely fine scale. The digital elevation model (DEM) was produced using LiDAR. The processing of DEM to delineate watersheds was accomplished using the different ArcHydro tools. The water is forced to drain by altering the DEM to represent green infrastructure, buildings, gutters and inlets.
Precipitation data collected onsite by Villanova Urban Stormwater Partnership (VUSP) is being used model a range of different storms to the GI capture, function and response. The model will be tested against other hydrologic parameters collected by VUSP at the study site; such stormwater pipe flow data. The gained understanding of the role of GI in a stormwater network from this project will contribute to improved stormwater management - helping to mitigate floods and improve downstream urban water quality.

Darby Creek is an urbanized highly flood-prone watershed in Metro-Philadelphia, PA. The floodplain and the main channel are composed of alluvial sediment and are subject to frequent geomorphological changes. The lower part of the channel is within the coastal zone, subjugating the flow to a backwater condition This study applies a multi-disciplinary approach to modeling the morphological alteration of the creek and floodplain in presence of the backwater using an iteration and integration of combined models. To do this, FaSTMECH (a two-dimensional quasi unsteady flow solver) in International River Interface Cooperative software (iRIC) is coupled with a 1-dimensional backwater model to calculate hydraulic characteristics of the flow over a digital elevation model of the channel and floodplain. One USGS gage at the upstream and two NOAA gages at the downstream are used for model validation. The output of the model is afterward used to calculate sediment transport and morphological changes over the domain through time using an iterative process. The updated elevation data is incorporated in the hydraulic model again to calculate the velocity field. The calculations continue reciprocally over discrete yearly peak discharges from 2006 to 2016. The results from this study demonstrate how to incorporate bathymetry and flow data to model floodplain evolution in the backwater through time, and provide a means to better understanding the dynamics of the floodplain. This work is applicable to river management, but also provides insight to the geoscience community concerning the development of landscapes in the backwate

The redesign of Interstate-95 through Philadelphia is a multi-decade and multimillion-dollar reconstruction project. Stormwater management is being included in the highway redesign plans where none existed before due to current regulations. Villanova and Temple Universities hold a grant with PennDOT and AECOM to attempt to further understand the unit processes that control bioswale and SMP performance in an urban transportation setting through scientific water quantity and quality monitoring. It is expected that this understanding can help with future SMP designs; to reduce water quantity entering the storm sewer system and adjust design standards to possibly lower the SMP cost per unit area.
This research analyzes the ability of the US EPA Stormwater Management Model (SWMM) to replicate the measured performance of three linearly adjacent bioswales for the period of March 2017 through July 2017. The bioswales are located along I-95 in Philadelphia and are receiving direct runoff from the adjacent elevated highway. Components of this research include instrumentation design and setup; and modeling the hydrology of the capture area, hydraulics of the piping system, and the performance of the bioswales.

Impervious surfaces generate large volumes of runoff during rainfall events, putting stress onto natural receiving streams and combined sewer overflow systems. Green stormwater infrastructure or just green infrastructure is a newer best management practice that is implemented to reduce stormwater runoff depth and improve stormwater quality before it is released to a receiving body of water. This study seeks to monitor environmental parameters and the runoff condition of a 9-acre parking lot on Villanova University’s campus before it is developed into a student housing facility. After development is completed, the site will be equipped with an extensive green infrastructure stormwater management system. The goals of this study are to obtain an understanding of the hydrology of the parking lot during storm events, determine stormwater quality during the first flush and average for the event, groundwater levels and vertical temperature profile over an impervious surface or the presence of an urban heat island effect.

In trying to deal more effectively with urban stormwater runoff, recent research has been focused on implementing smart stormwater systems that optimize volume collection and removal performance. Several green infrastructure technologies on the Villanova University campus have been recently retrofitted to include real-time control to achieve this improved volume removal goal. These systems utilize the physical processes present in green infrastructure (infiltration, evapotranspiration, etc.) to manipulate the hydrologic timing to optimize performance through actively controlled inflows and discharges from the system. The control is implemented through a cloud-native platform developed by OptiRTC, a technology firm focused on control of stormwater infrastructure.

A modeling study was completed of a real-time controlled green and gray roof system on the Villanova University campus. The study site is comprised of an existing extensive green roof and an adjacent gray roof that has been retrofitted to capture excess runoff from the system. Stored runoff is actively released onto the green roof during dry periods to fully utilize the evapotranspiration potential of the green roof while increasing total capture from the system. The system as a whole demonstrates how forecast information, remote sensing, and self-learning components can be integrated into a green infrastructure system to optimize performance. The long-term continuous simulation compared performance of the green roof system to the performance prior to being retrofitted, allowing for the benefit of the real-time control to be evaluated.

Quantifying evapotranspiration (ET) and infiltration from vegetated stormwater control measures (SCMs), such as rain gardens, is necessary to properly assess their volume reduction potential. A standard model equation in most states or regulatory entities is used for rain garden design which only includes static processes and excludes the dynamic functions of infiltration during an event and ET during the time between events. Weighing lysimeters on Villanova’s campus are used to assess the mass balance determine ET in rain garden designs. Soil moisture meters and predictive ET equations are found to be adequate proxies of observed ET as an effort to incorporate ET into design.

With increasing world populations, it becomes necessary to better understand the impacts of human activities on the environment. Robust environmental detection and characterization systems enable greater understandings of such systems and ultimately allows human interventions to be designed in a more sustainable manner. This presentation will seek to be an informative resource for implementing robust environmental detection and characterization systems for individuals with minimal background in this area.

At Villanova University, a Constructed Stormwater Wetlands (CSW) was designed to reduce nutrient concentration and attenuate flow entering the headwaters of Mill Creek, a tributary of Schuylkill River. For several years, studies have been conducted on the overall performance of the CSW, but there has not been enough data until now to discern performance changes over time and the parameters that influence these changes. This presentation focuses on analyzing the flow entering and leaving the CSW from 2012 to 2016 as well as the impacts caused by climate conditions on the overall effectiveness of flow attenuation. Additionally, Total Suspended Solids (TSS) concentrations are analyzed to determine whether it is an indicator of first flush and can be used as a decision maker in “smart” SCM systems (i.e. real time control).

The use of green stormwater infrastructure (GSI) continues to grow as an important source of stormwater management in cities across the United States. Designing GSI systems often includes implementing pretreatment practices to avoid clogging, reduce maintenance, and increase the life span of the infrastructure. Often, arbitrary design guidelines are adopted for these pretreatment practices with unknown impact on the longevity and performance of the subsurface systems. This is due to a lack of information on the local stormwater runoff characteristics, particularly particle size distribution. This preliminary study outlines a methodology by identifying site selection, sampling procedures, and measurement device selection to ultimately better understand GSI performance in Philadelphia. By sampling two Philadelphia stormwater management practices (SMPs) during simulated runoff tests (SRTs) and natural rain events at set sampling locations throughout the stormwater flow path in the SMP, local stormwater particle size distribution is analyzed. Total suspended solids, turbidity, and conductivity analyses were also conducted. These analyses are intended to indicate the effectiveness and performance of these SMPs and indicate if alterations of pretreatment protocols are needed for Philadelphia SMP design.

Rain gardens and other bioretention stormwater control measures (SCMs) have proven to be an effective means to mitigate increased stormwater runoff. Present rain garden design and research has focused on infiltration as the key volume reduction mechanism, but the inclusion of evapotranspiration (ET) in the design of SCMs is a viable removal method. Design guidelines for soil types in rain gardens are often restrictive, but tailoring the soil media to site specific conditions, or using on-site soils, to promote either infiltration or ET can be beneficial to increase both volume and pollutant removal. A bench scale study was designed at Villanova University to assess the quantity and quality removal capabilities of five different USDA soil types. This study will focus on investigating and quantifying two design parameters for vegetated SCMs, soil type and flow path, to maximize volume and pollutant reduction. It is hypothesized that the optimal balance between infiltration and ET for site-specific conditions will enable optimized volume and pollutant removal.

A rain garden on Villanova University’s campus, commonly referred to as the Bioinfiltration Traffic Island (BTI), has been studied extensively since its construction in 2001. While inflow and overflow estimations have been verified and provide total removal volumes, less is known about how much is removed by deep infiltration (water that reaches the groundwater table) and how much by evapotranspiration. The goal of this research is to develop a better understanding of the deep infiltration through the rain garden and develop a method to estimate this volume. Past studies on the groundwater table at the site have found that storms over 0.71 inches produce a mound directly below the rain garden. By further investigating the groundwater mounding, infiltration removal volumes will be estimated. Data collected from observation wells, soil moisture meters, a weather station, and water level sensors will be used to calibrate a two-dimensional model of the rain garden using the Hydrus software package. This model will provide a better idea of the extent of the mound and the infiltrated volume that contributes to it.

Once infiltration volumes have been calculated, the only unknown variable remaining in the water balance equation will be evapotranspiration. The volume of runoff that does not overflow from the system or contribute to groundwater recharge will be available to evapotranspiration and, using a mass balance, the evapotranspiration can be estimated. The volumes of each component of the water balance will vary based on storm type, environmental factors, time between storms, etc. By understanding these factors, a method can be developed to continue to calculate the internal storage and evapotranspiration at the site in the future. This information can aid in the design of more efficient green infrastructure which is especially important in urban settings where space is limited.

The issue of combined sewer overflow (CSO) caused by urbanization and increased imperviousness within urban watersheds is attempted to be solved by decentralized stormwater management facilities. However, available space is one of the limiting factors when planning and designing urban stormwater control measures (SCMs). Infiltration trenches can be placed underneath developed sites and have been shown to minimize runoff volume and peak flows as well as improve water quality and provide groundwater recharge, but there is limited data available on the effectiveness and longevity of these SCMs.

This presentation will discuss how failure occurred in an infiltration trench that went online in 2004 and experienced diminished performance after one year of operation. Excavation and forensic analysis of the infiltration trench in Fall 2015 indicated that failure occurred due to the buildup of fine-grained particles in the influent manifold and at the geotextile/soil interface.

Based on these findings, a pretreatment system (Contech JellyfishÒ) was added as part of the infiltration trench retrofit (which went online in July 2016) to remove particulates from the runoff before entering the infiltration trench. Additionally, a modular stormwater storage system (ACF Environmental R-Tanks®) replaced the stone aggregate as the storage media inside the trench to facilitate ease of maintenance and increase the lifetime of the infiltration trench. How these modifications affect the performance of the infiltration trench with respect to stormwater volume reduction, infiltration trench recession rate and water quality improvement will be discussed as well.

Rainfall is the primary source of uncertainty in many hydrologic models. To minimize this uncertainty, an ideal rain gauge is both local to the site being evaluated and a high accuracy instrument. Many times, such an ideal rain gauge does not exist. The goal of this research is to increase understanding of how an imperfect rain gauge influences analysis of a particular flow regime. To complete this task, four versions of an US Environmental Protection Agency’s (EPA) Storm Water Management Model (SWMM) are being created for the East Branch of Indian Creek Watershed in Narberth and Lower Merion, Pennsylvania. All aspects of the four models will be the same, except that each model will be calibrated to a unique rain gage. The four uniquely calibrated models will then be used to evaluate the flow regime for a typical water year. It is expected that the distinctions in the flow regimes for the four models will demonstrate how the imperfections associated with each rain gauge alters the user’s understanding of the health of the watershed.

This research is part of the Delaware River Watershed Initiative (DRWI), funded by the William Penn Foundation. Therefore, it is assumed that the model being evaluated in this study will ultimately be used to evaluate the success of stream restoration efforts. Thus, this research ultimately aims to provide insight into the extent to which an imperfect rain gauge will alter the researcher’s understanding of restoration success in terms of water quantity.

The National Water Model (NWM) provides a platform needed to operationalize nationwide flood inundation forecasting and mapping. The ability to model flood inundation on a national scale will put invaluable information into the hands of decision makers and local emergency officials. However, forecast products use deterministic model output to provide a visual representation of a single inundation scenario, which is subject to uncertainty from various sources. The goal of this study is to quantify and visualize uncertainties associated with the predicted flood inundation maps. The setting for this study is the highly urbanized Darby Creek watershed \ Darby Creek in metro-Philadelphia. A forecasting framework incorporating the NWM coupled with multiple hydraulic models was developed to produce ensembles of future flood inundation conditions. International River Interface Cooperative (iRIC) and HEC-RAS were used to quantify the agreement between output ensembles for each forecast grid provided the uncertainty metrics for predicted water extent, depth, and flow velocity. For visualization, a series of flood maps that display flood extent, water depth, and flow velocity along with the underlying uncertainty associated with each of the forecasted variables were produced. The results from this study demonstrate the potential to integrate and visualize model uncertainties in flood inundation maps in order to identify the high flood risk zones with critical thresholds.

Road de-icing salt is one contaminant of concern in stormwater runoff, as it has been shown to have negative effects on plant and animal species, decrease biodiversity, and degrade environmental quality. It has been assumed that road de-icing salt would wash through watersheds with spring rains, as road salt (usually NaCl) is soluble, and chloride (Cl-) has long been considered a conservative tracer. However, many recent studies suggest that significant proportions of chloride mass may be retained within a watershed and that chloride levels resulting from winter salting activities may remain elevated late into summer months. Stormwater control measures (SCMs) have been praised for both volume reduction and improved water quality, but recent studies are showing that certain SCMs may increase the negative effects of road salting on the surrounding environment, such as contamination of groundwater, trace metal leaching, stratification in ponds, toxic effects, and reduced biodiversity. Because chloride poses a possible threat to downstream waters, a study was performed to study the fate and transport of chloride through a constructed stormwater wetland (CSW), on Villanova’s campus.

The study had these main goals: i.) to determine if effluent concentrations of chloride from the CSW meet recommended EPA standards for chronic and acute criteria and ii.) to perform a mass balance of chloride upstream, within, and downstream of the CSW. Chloride concentrations were observed over a period of four years, from December 2011 - November 2015 and a mass balance was done with flow data for 2013 and 2014.

Sustainable infrastructure research has led to an increase in the use of stormwater control measures (SCMs). Rain gardens are vegetated SCMs which promote infiltration, evapotranspiration, or both. As the use of rain gardens and other sustainable practices becomes more common, cost effective techniques are needed to determine site properties for design and to assess their performance after construction. A major component of rain garden performance is hydraulic conductivity, which can be determined by infiltration testing. The double-ring infiltrometer test, while commonly used in practice, can take long periods of time to complete. Single-ring infiltrometer tests often use less water and require less time to implement, enabling more tests to be completed in the same period of time.

Seven small single ring infiltrometer tests were performed at a rain garden on Villanova’s campus in Fall 2014 to determine the field hydraulic conductivity of surficial soil in the SCM. The instrumentation at the site used in the field study has been recording the recession rate in the pond over the past twelve years. Comparing the pond recession rate to the field hydraulic conductivity, it was found that the less commonly used single-ring infiltrometer method can be an accurate predictor of SCM performance.

Storm water management is a major concern for cities with outdated combined sewer systems. Uncontrolled storm water pollutes urban watersheds, and impairs ecological functions in streams and rivers. Evapotranspiration by trees is expected to be a significant GI component that diverts water from sewer systems, and storm water interception by green infrastructure (GI) installations with urban trees will likely be a major contributor to improving overall runoff control. It is important to assess the performance of these trees to better understand their contributions to storm water management.

The first research project has focused on water relations of trees in a GI tree trench system in the Mt. Airy section of Philadelphia. Acer rubrum ‘Armstrong’ and Platanus × acerifolia ‘Bloodgood’ were evaluated from May through November for stomatal conductance, leaf water potential (Ψlf) and leaf area index (LAI). Water relation trends were evident, and a one-way ANOVA with post-hoc Tukey HSD test showed a significant difference between stomatal conductance rates of the two species, but not within species. Analysis of Ψlf data was performed using a Kruskal-Wallis test rank sum test followed by Dunn’s test of multiple comparisons. These analyses also showed significant differences between the ranked data of the two species. In general, through the entire growing season, P. × acerifolia had greater stomatal conductance and lower susceptibility to water stress than A. rubrum ‘Armstrong’.

A second research project has evaluated the stomatal conductance of 25 trees of 13 different species/cultivars located at the same site. The trees were monitored from June-October 2015. In the preliminary analyses, tree species exhibited significantly different levels of stomatal conductance throughout the season, implying that some species are better suited as urban stormwater trench trees than others. Furthermore, pairwise t-tests reveal that Koelreuteria paniculata and Prunus sargentii trees consume significantly more water within stormwater trenches compared to traditional, isolated tree pits, whereas Quercus macrocarpa trees showed the opposite tendency.

This research not only confirms that stormwater tree trenches can be effective at managing stormwater but it also holds implications for further application of stormwater tree trenches since the selection of tree species can determine the effectiveness of the system.

Infiltration trenches are stormwater control measures (SCM) that are designed in urban, residential or commercial areas to temporarily store and treat stormwater runoff by infiltration. These SCMs can provide significant runoff volume reduction, groundwater recharge and can also help with nutrient removal through soil sorption and filtration. Especially in highly urban areas where space is limited, underground infiltration trenches are well suited to help fulfill current stormwater regulations and prevent flooding. However, not much data is available on long-term performances, longevity and effectiveness with respect to suspended solids and nutrient removal.

In 2004, an infiltration trench was constructed on campus at Villanova University to capture runoff from a 100% impervious drainage area (parking deck). The trench was significantly under-designed with an SCM surface area to drainage area ratio of 160:1 (5:1 recommended by most BMP manuals). The highly increased loading of suspended solids and debris, quickly decreased the system's performance and recession rates dropped just one year after being set online. The old trench was then excavated in October 2015 and a forensic analysis of sediments inside the trench and the surrounding soils was performed to assess the eventual failure of the system.

A new infiltration trench with a pretreatment system was constructed at the same location with the exact same footprint but a smaller SCM surface area to drainage area surface (40:1). Water quantity and quality instrumentation of the new trench are currently being installed. The new system is planned to be set online and monitored in fall 2016.

Rain gardens have proven to be an effective means to control stormwater; thus, in Pennsylvania’s Stormwater Best Management Practice’s Manual, rain gardens are the preferred stormwater control measure (SCM). Currently, volume capture in Pennsylvania is calculated using a static bowl equation that does not include the dynamics of infiltration and evapotranspiration (ET). In addition, many states’ design guidelines for rain garden soil mixes are often restrictive and vague. The goal of the work described in this presentation is to develop guidelines for soil mixes that consider the balance of infiltration and ET using bench-scale experiments at Villanova University. A total of twelve discrete weighing lysimeters were filled with soils that span the lower portion the USDA classification triangle. The lysimeters were divided evenly into two flow path configurations: vertical 46 cm deep columns and horizontal 20 cm deep boxes at a 2.5% slope. Both lysimeter configurations utilized loamy sand, sandy loam (typical rain garden mix in PA), loam, silt loam, and clay loam soils. Switchgrass was planted in all but two lysimeters to provide a non-vegetated control with sandy loam soil. Runoff was added into the lysimeters during rainfall events to simulate actual rain garden performance and the lysimeters were weighed daily for two weeks after the event. Preliminary results of five storm simulations provide an average ET rate of 3.3 mm/d for the vertical lysimeters and 2.6 mm/d for the horizontal lysimeters. In the vertical configuration the silt loam soil produces the most volume removal through ET at 44% of the total volume removal with an average ET rate of 4.2 mm/d. In contrast, the loamy sand soil produces the least volume removal through ET at 25% of the total volume removal.

Accurately monitoring stormwater control measurements (SCMs) in the urban environment is extremely difficult because conditions are variable, space is limited, there is the potential for vandalism, and the normal flow of urban life cannot be interrupted. Outside of seasonal variability, monitoring equipment is subjected to harsh conditions with trash, sedimentation, debris, and vandalism that may disrupt the performance of monitoring equipment and the SCM. An investigation is conducted to analyze the differences in accuracy between ideal laboratory settings and urban field conditions. The purpose of this research is to select the most appropriate monitoring equipment for urban SCMs and analyze the accuracy of sensors. The focus is on the inflow and outflow structures of two different urban SCMs (i.e. rain garden and tree trench) a part of Philadelphia Water Department’s Green City, Clean Waters. The accuracy and reliability of monitoring equipment is determined with laboratory experiments. Ultimately, the goal is to implement the best suited equipment in the field that will record the most accurate data. This presentation involves the analysis of existing equipment supplied by manufacturers, and also requires thinking outside the box for typical flow measurement devices, including the development of new approaches to accurately monitor flow.

Stormwater control measures (SCMs) are used in urban and suburban areas to control runoff volume and peak flow rates, as well as improve the quality of runoff water. Rain gardens are one type of vegetated SCM which can contain engineered or native media. A major component used in design and performance of SCMs and rain gardens is hydraulic conductivity, which can be measured in the field using various infiltration testing techniques. Infiltration testing can be performed during initial site investigations to determine the appropriate SCM design and performed post-construction to ensure the SCM is performing well. The most common infiltration testing technique used in industry is the double-ring infiltrometer (ASTM D3385). However, this technique can be cumbersome because the infiltrometers are large and require a great deal of energy to install and a large quantity of water to perform.

In this study, the authors employed various infiltration techniques to determine the in-situ hydraulic conductivity at various sites. These sites included rain gardens of varying ages with engineered media, as well as a site with native soils where test pits were dug during an investigation to determine future SCM design. The authors built a Modified Philip-Dunne Infiltrometer and compared it to other field methods such as the double-ring and single-ring infiltrometer. Additionally, a falling-head PVC pipe test was designed by the authors and is also used in the comparison study. The in-situ measurements obtained with the Modified Philip-Dunne test was also compared to laboratory values obtained with the UMS KSAT Benchtop Saturated Hydraulic Conductivity Instrument, which complies with DIN 19683-9 and DIN 18130-1. Preliminary results indicate that the Modified Philip-Dunne provides results similar to the other tests methods, producing hydraulic conductivities in the same order of magnitude or within one order of magnitude as the other methods.

Every year thousands of tons of rock salt are used as a deicing agent in the winter and spring months to control snow and ice in the state of Pennsylvania. Although chloride ions are naturally occurring in the natural environment, this additional chloride becomes part of the water system once the snow and ice melt. Rain gardens, which are increasingly being used to control stormwater, divert runoff, and allow infiltration and evapotranspiration to restore the hydrologic cycle that was disrupted by development. In the winter months, however, rain gardens concentrate chlorides and there is concern about the effect these chlorides may have on the rain garden soils and groundwater beneath these infiltration features. To determine if the chloride concentrations in the rain garden soils and the groundwater beneath a rain garden at Villanova University were elevated, conductivity was measured. Surface water samples were taken of inflow and ponding water, conductivity probes at various depths were installed in the soil, and groundwater probes were installed to monitor the vertical movement of chlorides. Preliminary results indicate that chloride ions are elevated during winter and spring months, as evidenced by spikes in conductivity in both soil and groundwater. The elevated levels remain days to months after the deicing season, and the chloride concentrations in the soil do not completely return to baseline conditions, even in the summer. Groundwater conductivity values will be evaluated seasonally to determine if the rain garden is causing a chloride plume during the winter.

Abstract: Philadelphia has been installing green infrastructure across the city to help manage the increasing demand on existing stormwater infrastructure, as a part of the Green City Clean Waters plan. In order to verify that the green infrastructure that is being installed is effective in decreasing the load on the combined sewer system the sites need to be monitored. To help accomplish this, low cost data loggers were developed for use in unpowered and disconnected sites. While the initial data loggers have been successful in collecting data, there are many improvements that can still be made. This presentation will cover topics like the need for monitoring Green Infrastructure sites, the technology used to do so, successes and failures in the initial field deployment, and future directions.

Recent studies on green roof water quality have indicated that extensive green roofs are a source of phosphates, and occasionally nitrates, as compared to conventional roofing systems. However, due to the presence of soil media and vegetation, green roofs should be compared to other vegetated sites, as opposed to conventional roofs, for a fairer comparison. In this study, the impact of green roofs on surface water quality is placed in the context of other vegetated land uses, including two types of stormwater control measures (SCMs) as well as non-SCM sites. Site runoff and SCM effluent were evaluated for nitrogen and phosphorus species, chlorides, total suspended solids, and total dissolved solids. Comparisons of concentrations against EPA recommended criteria suggested that the green roof generally retained nitrogen and released phosphorus. Its performance was similar to that of a wooded area, a grassy area, and a mixed-use area, while it was outperformed by a rain garden and a constructed stormwater wetland.

To better gage the effect of the green roof’s volume retention performance on its water quality impact, a nutrient mass balance was conducted for the green roof, and mass loads for the comparison sites were calculated. Mass balance estimation suggests that the green roof’s water quality impacts could be mitigated by its volume retention capabilities. The green roof exports less nutrients than are input to the system from fertilization and atmospheric wet deposition, although overall it exports more than wooded areas, based on drainage area-scaled values. Findings may be used to guide land use planning including implementation of green infrastructure and management of urban green spaces. It is suggested that if nutrient export is a concern and space is available, green roof overflow could be diverted to other SCMs which are designed to remove excess nutrients from stormwater runoff.

Abstract: Green roofs are becoming increasingly popular as urban stormwater control measures (SCMs). Further understanding of the relation between design characteristics, like media depth and vegetation type, and stormwater performance is crucial to effective green roof design. The VUSP’s newest on-campus research site is a green roof shelter, designed to optimize stormwater volume reduction with a small footprint. The semi-intensive modular green roof is a living laboratory for stormwater research and community education. The research focuses on green roof performance for different configurations of growing media, plants, drainage designs and more. The monitoring system includes a custom orifice restricted device (ORD) designed to measure the relatively small magnitude of overflow. The presentation will give an overview of the shelter design and construction process, monitoring system implementation, data logging system, target research questions and STEM outreach.

As stormwater infrastructure becomes an ever increasing priority in site development, property owners and designers are becoming increasingly tasked with mitigating stormwater in creative ways. While many other sectors of infrastructure and development have embraced new technologies and worked with other branches of engineering, stormwater management has been stuck with the age old practice of infiltration. Unfortunately designers have been held back by outdated design regulations that have been slow to adopt the latest research in their guidelines.

A recent grant through the NSF will allow Villanova University to retrofit 3 of its on campus SCMs with some of the latest technology for stormwater management. In partnership with OptiRTC and The University of Pennsylvania, Villanova will be retrofitting The Green Roof Research Site, The Constructed Stormwater Wetland, and The Treatment Train in order to increase their performance as well as to study maintenance programs for stormwater infrastructure. The benefits of this technology can help downsize traditional SCMs, help ensure an SCMs longevity and continued performance, as well as drive down costs of installation and long term maintenance. This presentation will explore the three sites above and discuss present and future modifications underway as well as goals and expected outcomes of the project.

Low Impact Development (LID) or Green Infrastructure (GI) stormwater practices are gradually gaining acceptance in the United States. These practices are also being used to control stormwater in Ireland, where they are dubbed Sustainable Drainage Systems (SuDS). This talk will describe the observations made by the author about the status of SuDS in Ireland.

Road de-icing salt is one contaminant of concern in stormwater runoff with an estimated 15 million tons of salt being applied to U.S. roads every year. Road salt (usually NaCl) is soluble, and chloride (Cl) is a conservative tracer, meaning that it will not degrade over time. While many assumed that road de-icing salt would wash through watersheds with spring rains, as much as 77% of chloride has been shown to be retained within a watershed (Liptak and Mitsch 1996-98) and chloride levels may remain elevated late into summer months (Gardner and Royer 2010). Chloride has been shown to affect the survival and health of many amphibians at heightened levels (Karraker and Gibbs 2011) and increased chloride concentrations has resulted in increased metals concentrations (Endreny et al 2012). Because chloride poses a possible threat to downstream waters, a study was performed to study the fate and transport of chloride on Villanova’s campus.

The study aims to do a mass balance of chloride over two years in Villanova University’s constructed stormwater wetland (CSW) from the campus’ impervious surfaces, through the wetland, and into Mill Creek (the natural downstream waters) to see if there is any net retention or export of chloride. In addition, concentrations of chloride taken at intervals over a four year period for both storms and base flow events are compared to EPA chloride freshwater recommended standards to determine if Villanova’s CSW outflow meets that criteria. Correlations for TDS, conductivity, and chloride concentration are created in the course of this study and equations were formed to compare values of TDS, conductivity, and chloride. A unique k value for the CSW was determined for the equation Conductivity = k * TDS. The study aims to educate about the fate of road de-icing salts to inform sustainable action moving forward.

The three main components that determine the performance of a rain garden are the inflow volume, the size of the rain garden, and the soil hydraulic properties. Because soil hydraulic properties are often difficult to determine, proxies such as soil textural class or hydrologic soil group are often used instead of actual properties. The use of class-average soil properties for these proxies is a persistent practice in water resources engineering, but the effect of this practice has not been assessed or validated for use in rain garden design. This research uses a large dataset of soil hydraulic properties along with computer simulations of a rain garden to determine the effectiveness of these soil proxies for rain garden designs, specifically showing whether such proxies can determine the need for an underdrain, the effectiveness of fill media, and the overall expected performance of rain gardens during a design storm.

Abstract: Constructed Stormwater Wetlands (CSWs) are one type of Stormwater Control Measure (SCM) to treat stormwater runoff. The main objective of this research is to analyze the fate and transport of phytoplankton (i.e. free floating algae) in the Villanova University Constructed Stormwater Wetland (VU CSW). The VU CSW receives runoff from the Main and West campus and this runoff contains nutrients such as nitrogen and phosphorus which contribute to the algae growth, and hence, leads to eutrophication of the VU CSW. It also produces a measurable amount of algae during baseflow conditions that are washed away during storm events.

The concentrations of chlorophyll a (an indicator of algal content), dissolved oxygen, organic matter, temperature and nutrients in the VU CSW will be presented in an attempt to correlate algae growth with nutrient depletion. In addition, the mass of algae washed from the wetland during storm events will be quantified to determine if this export of algae may have a negative effect on downstream water quality.

Abstract: Over the past several decades research for green stormwater infrastructure (GSI) has been successful in demonstrating proof-of-concept and has resulted in large cities investing in large-scale GSI implementation projects that will span decades. While proper design, installation, and regular maintenance practices have evolved, there are still a lot of questions and assumptions made regarding the longevity and end-of-life of GSI systems. Using a multiple life cycle perspective, the potential cost and environmental impact savings of GSI “renewal” – as opposed to full decommissioning/replacement – are outlined for several stormwater control measures by incorporating elements of eco-efficiency, the Circular Economy, and industrial ecology. A “multi-generational approach” that aims to support the development of best practices for SCM design, maintenance, disassembly, and material reuse is broadly discussed. Recommendations are made for future studies that focus on extending the useful life of SCM materials.

A custom distribution system was built to simulate excess rain delivered to a rain garden during natural storm events. In Pennsylvania, SCMs are often sized to control a multiple (typically 5:1 for rain gardens) of a selected rain event. Trials were performed in April and August 2014 for half open controlled valve configurations. Both loamy sand and sand soils with a controlled valve configuration showed an average ET of 3.1 mm per day for 7 days after simulated 5:1 events. Sand soil with an IWS showed an average of 6.0 mm per day for 7 days after simulated 5:1 events. Simulated storm events produced larger ET rates, on average, than that of a 1:1 ratio. Comparisons of predictive equations show the ASCE Penman-Monteith under-predicting and Hargreaves over-predicting observed ET, but follows the trend of each lysimeter.

Abstract: The Morris Arboretum has one of the oldest porous asphalt sites in the country dating back to 1982. Today the asphalt is being replaced because it no longer infiltrates, and is wearing down. Because of this, the Villanova Urban Stormwater Partnership decided that it would be advantageous to perform a forensic study on the asphalt examining its current condition before replacement. The study focused on observing why the asphalt no longer infiltrates, quantifying the amount contaminants trapped in the asphalt, determining the asphalt's porosity and determining the asphalt's current infiltration rates. Results revealed high metal concentrations from the asphalt, low infiltration rates, and failure due to age and clogging.

Abstract:Stormwater control measures are built in order to address the issues of stormwater runoff. These issues are primarily focused around volume control and water quality treatment. Villanova University's Constructed Stormwater Wetland (CSW) was recently reconstructed in 2010 to improve treatment efficiency by adding meanders to hold runoff in the treatment system longer. From 2011 to present the CSW is sampled once to twice a month for storm and baseflow events. Until April 2014, sample collection for storms involved gathering samples 12 to 24 hours after rainfall ended. Though the flow rates during this time are still above average baseflows, the concentrations are not representative of first flush conditions. The use of automated samplers at the inlet and outlet permit for real time stormwater quality monitoring at the CSW. A comparison study between the grab sampling storms and autosampler events was performed, in addition to mass analysis for the automated samples.

Recent studies on green roof water quality have indicated that extensive green roof systems are a source for phosphorus, and occasionally a source for nitrogen as compared to conventional roofing systems. Due to the presence of soil media and vegetation on green roofs, a comparison to traditional roofs reveals little about relative nutrient quantities released. The Villanova green roof was compared to other suburban vegetated areas for nutrient export. The water quality parameters evaluated included nitrogen and phosphorus species, chlorides, total suspended solids, and total dissolved solids. Where applicable, US EPA recommended nutrient criteria for rivers and streams, and for lakes and reservoirs, were used as a reference point to nutrient parameters. Results indicated that the green roof generally retained nitrogen and released phosphorus; its performance was similar to or better than that of a grassy area and a wooded area in terms of nutrient retention, and performed similarly to an area that was at least 50% impervious. In addition, a comparison of quality data from overflow samples revealed that a nearby wetland and rain garden outperformed the green roof in terms of nutrient retention. It is suggested that if nutrient export is a concern and space is available, green roof overflow could be diverted to other stormwater control measures which are designed to remove excess nutrients from stormwater runoff.

Rain gardens are vegetated stormwater control measures (SCMs) that reduce runoff volume and high peak flows. Rain gardens promote infiltration and evapotranspiration (ET), thus mitigating the effects of high stormwater runoff that have become common in developed areas. In addition to runoff quantity, rain gardens also help improve water quality by allowing water to infiltrate into an engineered or native soil media. Engineered soils typically contain a high sand content with lower amounts of silts, clays, and organics. Native soils can be used if the hydraulic properties indicate that an adequate infiltration rate is attainable. Additionally, to save construction costs, engineered soils can be mixed with native soils. Rain gardens may also contain a liner and an underdrain. Systems without a liner allow for evapotranspiration and infiltration into the native soil layer, which promotes recharge to the underlying aquifer. Systems with a liner and underdrain typically favor evapotranspiration.

A study was proposed to determine the best rain garden design and configuration for optimum hydrologic performance. This included the use of a liner, the use of an underdrain, soil media, and age of the rain garden. Many rain gardens on Villanova University’s campus were considered, and three rain gardens were selected: the Bioinfiltration Traffic Island, Fedigan Rain Gardens, and Pavilion Traffic Island. The three sites have notably different configurations, soil mixtures, and other defining characteristics. After site investigations, instrumentation was selected for each site, which included pressure transducers, soil moisture sensors, and rain gages. This talk will describe the challenges and soil properties encountered during the site investigations, as well as the process of instrumentation and equipment selection for each site.

Funded by the EPA Urban Waters Small Grant program, the project's purpose is to design, construct and monitor two shelters (e.g. bus shelter or picnic table covering) with vegetated roofs in the Darby Creek watershed in southeastern Pennsylvania. The shelters will be living laboratories used for community education and stormwater research. The research component will focus on green roof performance for different configurations of growing media, plants, drainage designs and more. The education component includes collaboration with the Eastern Delaware County Stormwater Collaborative and Upper Darby High School to introduce community members to green roof technologies and introduce students via the science curriculum to the hydrologic processes of green roofs.

A key component of these living laboratories is to precisely and accurately measure the inputs and outputs of the green roof to quantify performance. The magnitude of outflow (drainage) measurements is relatively small for these small-scale green roofs, thus requiring a custom solution to measure outflow. The presentation will give an overview of the project goals and also focus on the method developed for runoff measurement from the green roofs.

Infiltration trenches are a stormwater control measure (SCM) used in urban and ultra-urban areas to provide stormwater runoff volume reduction. Legacy infiltration trenches are difficult if not impossible to maintain and were often built without pretreatment. As runoff with high suspended solid loads enters an infiltration trench there is continual buildup of solids that clog the infiltrating surface, decreasing the hydraulic conductivity at the soil interface and the performance and longevity of these systems.

The present study builds on previous work at Villanova University on an extremely undersized infiltration trench (directly connected impervious drainage area to SCM area of 160:1) to artificially accelerate annual loading to evaluate long-term performance. Ten years and 1270 cm of rain later, infiltration through the bottom of the trench has ceased and the sides have slowed as well. Recession rates have reached an equilibrium point where they no longer improve or decrease. Although recession rates have slowed considerably since 2004, reduced infiltration still occurs in the bottom layer of the IT.

Green roofs are an effective, yet costly stormwater control measure that reduces runoff volume through ET, and can provide other services, such as improved building insulation and reduced urban heat island effect. For green roof systems to be competitive as a low impact development strategy, they must be designed to maximize ET. Understanding each component’s process in a green roof design is the key to designing a green roof to perform optimally.

Evapotranspiration (ET) is a primary mechanism for removal of water in a green roof. When adequate water is available, the ET rate is limited by the energy-available. However, when the system is water-limited then less ET will occur than is climatologically possible, thus causing the green roof to perform sub-optimally. One way to retain more water within the green roof is to minimize drainage (outflow) by altering or restricting the drainage layer within a green roof. In the present work, a green roof with a drainage layer is compared to a lysimeter without a drainage layer to determine if hydrologic performance is enhanced or compromised in either system.

Preliminary results from the Villanova University green roof systems show that the under drained system has approximately 65% of rainfall go to ET, while the undrained system showed 77% ET from April through November 2013. However, the system without drainage has seen as high as 88% annually go to ET in drought years. Additionally, the plants appeared healthier during the drought in the undrained system than in the drained system.

Disclaimer: The VUSP graduate student presentations are intended to inform the VUSP community on ongoing research on Green Stormwater Infrastructure. The material is presented by students based on current ongoing research that is supported by a variety of grants, and as such should be viewed as a work in progress. Final results are available through thesis and externally reviewed journal articles.

Student presentations have been recorded since late 2009. These presentations can be found here.

VUSP is one of the five research areas that constitute the Villanova Center for the Advancement of Sustainability in Engineering (VCASE).

VCASE hosts lecture series during Fall and Spring semesters and invites external people to give a talk related to sustainability issues. One can view these talks either online or can plan to attend in person.